The effect of ascorbic acid deficiency on serum levels of high density lipoprotein- (HDL-), low density lipoprotein- (LDL-), very low density lipoprotein- (VLDL-) and chylomicron-cholesterol was examined in ODS-od/od rat (ODS rat), that is a rat mutant unable to synthesize ascorbic acid. Male ODS rats were fed an ascrobic acid-free diet for 20 days. In another two groups, the diet supplemented with 300 mg ascorbic acid/kg diet was fed either ad libitum (ad libitum control) or in pair-feeding (pair-fed control). Pair-fed rats received the same amount of diet as rats fed the ascorbic acid-free diet. Serum level of total cholesterol in the ad libitum control rats, ascorbic acid-deficient rats, and the pair-fed control rats were 100.1 +/- 8.4 mg/dl, 92.8 +/- 6.2 mg/dl and 72.2 +/- 4.8 mg/dl, respectively. The level of LDL-cholesterol in ascorbic acid-deficient rats was significantly higher than that in the ad libitum control or that in the pair-fed control. The level of HDL-cholesterol in ascorbic acid-deficient rats was lower than that in the ad libitum control, but was not changed as compared with that in the pair-fed control. Ascorbic acid deficiency did not affect serum level of VLDL-cholesterol or chylomicron-cholesterol as compared with those in the controls. These results demonstrate that ascorbic acid deficiency causes the elevation of serum level of LDL-cholesterol both in ad libitum feeding condition and pair feeding condition.